Abstract

The operational atmospheric correction algorithm for Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) uses the predefined aerosol models to retrieve aerosol optical properties, and their accuracy depends on how well the aerosol models can represent the real aerosol optical properties. In this paper, we developed a method to evaluate the aerosol models (combined with the model selection methodology) by simulating the aerosol retrieval using the Aerosol Robotic Network (AERONET) data. Our method can evaluate the ability of aerosol models themselves, independent of the sensor performance. Two types of aerosol models for SeaWiFS and MODIS operational atmospheric correction algorithms are evaluated over global open oceans, namely the GW1994 models and Ahmad2010 models. The results show that GW1994 models significantly overestimate the aerosol optical thicknesses and underestimate the Ångström exponent, which is caused by the underestimation of the scattering phase function. However, Ahmad2010 models can significantly reduce the overestimation of the aerosol optical thickness and the underestimation of the Ångström exponent as a whole, but this improvement depends on the backscattering angle. Ahmad2010 models have a significant improvement in the retrieval of the aerosol optical thickness at a backscattering angle less than 140°. For a backscattering angle larger than 140°, GW1994 models are better at retrieving the aerosol optical thickness than the Ahmad2010 models.

E. P. Shettle and R. W. Fenn, “Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties,” Report No. AFGL-TR-79-0214(United States Air Force Geophysics Laboratory, Hanscom Air Force Base, 1979).

1979 (1)

E. P. Shettle and R. W. Fenn, “Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties,” Report No. AFGL-TR-79-0214(United States Air Force Geophysics Laboratory, Hanscom Air Force Base, 1979).

Fenn, R. W.

E. P. Shettle and R. W. Fenn, “Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties,” Report No. AFGL-TR-79-0214(United States Air Force Geophysics Laboratory, Hanscom Air Force Base, 1979).

E. P. Shettle and R. W. Fenn, “Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties,” Report No. AFGL-TR-79-0214(United States Air Force Geophysics Laboratory, Hanscom Air Force Base, 1979).

E. P. Shettle and R. W. Fenn, “Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties,” Report No. AFGL-TR-79-0214(United States Air Force Geophysics Laboratory, Hanscom Air Force Base, 1979).

Figures (8)

Accumulative frequencies of the selected aerosol models for 11 AERONET stations by (a) GW1994 models and (b) Ahmad2010 models. The sum of the frequency for each station is normalized to the unit. The index of the aerosol models corresponds to Table 2.

Comparison of the AOTs at 440, 675, and 870nm retrieved by the aerosol models and the in situ values for all the selected 11 AERONET stations. The dashed line is a 1∶1 line. The left panel contains the results of the AOTs retrieved by GW1994 aerosol models, while the right panel contains the results of the Ahmad2010 aerosol models.

Comparison of the Ångström exponent at 440nm retrieved by aerosol models and the in situ values for all the selected 11 AERONET stations. The horizontal lines in the boxes denote the twenty-fifth, fiftieth, and seventy-fifth percentile values; the error bars denote the fifth and ninety-fifth percentile values; the two symbols below the fifth percentile error bars denote the zeroth and first percentile values; the two symbols above the ninety-fifth percentile error bars denote the ninety-ninth and one hundredth percentiles; the solid square symbols in the boxes denote the mean value.

Comparison of the AOTs at 870nm retrieved by aerosol models and the in situ values for all 11 stations with backscattering angle less than 140°. The dashed line is a 1∶1 line. (a) GW1994 models; (b) Ahmad2010 models.

Comparison of the AOTs at 870nm retrieved by aerosol models and the in situ values for all 11 stations with backscattering angle larger than 140°. The dashed line is a 1∶1 line. (a) GW1994 models; (b) Ahmad2010 models.

Table 3 Mean Value and Standard Deviation of the AOT and Ångström Exponent Measured by AERONET and the Mean Bias and Standard Deviation of the AOT and Ångström Exponent Retrieved by the GW1994 and Ahmad2010 Modelsa

Table 3

Mean Value and Standard Deviation of the AOT and Ångström Exponent Measured by AERONET and the Mean Bias and Standard Deviation of the AOT and Ångström Exponent Retrieved by the GW1994 and Ahmad2010 Modelsa

Observation Station

τ(440nm)±σ

Δτ(440nm)±σ

τ(675nm)±σ

Δτ(675nm)±σ

GW1994

Ahmad2010

GW1994

Ahmad2010

Azores

0.094±0.055

−0.004±0.036

−0.005±0.032

0.058±0.036

0.008±0.020

0.007±0.017

Tudor_Hill

0.120±0.065

−0.011±0.046

−0.021±0.038

0.076±0.040

0.019±0.034

0.008±0.027

Ascension_Island

0.198±0.151

−0.001±0.076

−0.008±0.062

0.137±0.091

0.019±0.048

0.006±0.035

Midway_Island

0.096±0.053

0.008±0.035

−0.000±0.028

0.076±0.043

0.015±0.029

0.004±0.021

Lanai_Island

0.075±0.047

−0.003±0.031

−0.010±0.028

0.053±0.029

0.009±0.020

0.001±0.016

Guam_Island

0.072±0.022

0.000±0.024

0.000±0.026

0.053±0.018

0.005±0.018

0.002±0.016

Nauru

0.058±0.022

0.004±0.023

−0.001±0.022

0.047±0.022

0.008±0.022

0.001±0.017

Tahiti

0.058±0.028

−0.004±0.017

−0.005±0.018

0.042±0.020

0.002±0.012

−0.001±0.011

REUNION_ST_DENIS

0.058±0.032

−0.005±0.019

−0.009±0.017

0.038±0.018

0.008±0.013

0.003±0.011

Amsterdam_Island

0.061±0.033

0.005±0.025

−0.005±0.022

0.046±0.028

0.013±0.022

0.003±0.018

Crozet_Island

0.087±0.097

−0.009±0.042

−0.013±0.034

0.053±0.053

0.011±0.031

0.006±0.022

All 11 stations

0.090±0.081

−0.002±0.039

−0.008±0.033

0.064±0.053

0.010±0.026

0.003±0.020

Observation Station

τ(870nm)±σ

Δτ(870nm)±σ

α(440nm)±σ

Δα(440nm)±σ

GW1994

Ahmad2010

GW1994

Ahmad2010

Azores

0.047±0.030

0.006±0.014

0.003±0.013

1.067±0.341

−0.328±0.370

−0.242±0.340

Tudor_Hill

0.067±0.034

0.022±0.032

0.009±0.025

0.841±0.372

−0.601±0.338

−0.514±0.351

Ascension_Island

0.114±0.067

0.021±0.044

0.002±0.031

0.698±0.359

−0.227±0.341

−0.067±0.351

Midway_Island

0.071±0.040

0.015±0.027

0.001±0.019

0.471±0.275

−0.184±0.227

−0.050±0.266

Lanai_Island

0.047±0.023

0.009±0.017

0.001±0.013

0.629±0.366

−0.293±0.375

−0.192±0.392

Guam_Island

0.049±0.018

0.003±0.016

−0.002±0.012

0.612±0.251

−0.067±0.312

0.047±0.312

Nauru

0.044±0.022

0.007±0.021

−0.001±0.015

0.477±0.290

−0.140±0.379

−0.055±0.422

Tahiti

0.037±0.017

0.002±0.011

−0.003±0.010

0.688±0.291

−0.209±0.376

−0.084±0.386

REUNION_ST_DENIS

0.034±0.015

0.008±0.012

0.002±0.010

0.775±0.363

−0.461±0.326

−0.358±0.345

Amsterdam_Island

0.045±0.028

0.011±0.021

0.001±0.016

0.530±0.416

−0.328±0.428

−0.285±0.448

Crozet_Island

0.045±0.039

0.012±0.030

0.005±0.022

0.780±0.645

−0.579±0.544

−0.506±0.544

All 11 stations

0.056±0.042

0.018±0.024

0.004±0.017

0.662±0.364

−0.297±0.365

−0.183±0.385

a The minus and plus of the mean bias values represent the underestimation and overestimation by the aerosol models relative to the in situ values, respectively.

Table 3

Mean Value and Standard Deviation of the AOT and Ångström Exponent Measured by AERONET and the Mean Bias and Standard Deviation of the AOT and Ångström Exponent Retrieved by the GW1994 and Ahmad2010 Modelsa

Observation Station

τ(440nm)±σ

Δτ(440nm)±σ

τ(675nm)±σ

Δτ(675nm)±σ

GW1994

Ahmad2010

GW1994

Ahmad2010

Azores

0.094±0.055

−0.004±0.036

−0.005±0.032

0.058±0.036

0.008±0.020

0.007±0.017

Tudor_Hill

0.120±0.065

−0.011±0.046

−0.021±0.038

0.076±0.040

0.019±0.034

0.008±0.027

Ascension_Island

0.198±0.151

−0.001±0.076

−0.008±0.062

0.137±0.091

0.019±0.048

0.006±0.035

Midway_Island

0.096±0.053

0.008±0.035

−0.000±0.028

0.076±0.043

0.015±0.029

0.004±0.021

Lanai_Island

0.075±0.047

−0.003±0.031

−0.010±0.028

0.053±0.029

0.009±0.020

0.001±0.016

Guam_Island

0.072±0.022

0.000±0.024

0.000±0.026

0.053±0.018

0.005±0.018

0.002±0.016

Nauru

0.058±0.022

0.004±0.023

−0.001±0.022

0.047±0.022

0.008±0.022

0.001±0.017

Tahiti

0.058±0.028

−0.004±0.017

−0.005±0.018

0.042±0.020

0.002±0.012

−0.001±0.011

REUNION_ST_DENIS

0.058±0.032

−0.005±0.019

−0.009±0.017

0.038±0.018

0.008±0.013

0.003±0.011

Amsterdam_Island

0.061±0.033

0.005±0.025

−0.005±0.022

0.046±0.028

0.013±0.022

0.003±0.018

Crozet_Island

0.087±0.097

−0.009±0.042

−0.013±0.034

0.053±0.053

0.011±0.031

0.006±0.022

All 11 stations

0.090±0.081

−0.002±0.039

−0.008±0.033

0.064±0.053

0.010±0.026

0.003±0.020

Observation Station

τ(870nm)±σ

Δτ(870nm)±σ

α(440nm)±σ

Δα(440nm)±σ

GW1994

Ahmad2010

GW1994

Ahmad2010

Azores

0.047±0.030

0.006±0.014

0.003±0.013

1.067±0.341

−0.328±0.370

−0.242±0.340

Tudor_Hill

0.067±0.034

0.022±0.032

0.009±0.025

0.841±0.372

−0.601±0.338

−0.514±0.351

Ascension_Island

0.114±0.067

0.021±0.044

0.002±0.031

0.698±0.359

−0.227±0.341

−0.067±0.351

Midway_Island

0.071±0.040

0.015±0.027

0.001±0.019

0.471±0.275

−0.184±0.227

−0.050±0.266

Lanai_Island

0.047±0.023

0.009±0.017

0.001±0.013

0.629±0.366

−0.293±0.375

−0.192±0.392

Guam_Island

0.049±0.018

0.003±0.016

−0.002±0.012

0.612±0.251

−0.067±0.312

0.047±0.312

Nauru

0.044±0.022

0.007±0.021

−0.001±0.015

0.477±0.290

−0.140±0.379

−0.055±0.422

Tahiti

0.037±0.017

0.002±0.011

−0.003±0.010

0.688±0.291

−0.209±0.376

−0.084±0.386

REUNION_ST_DENIS

0.034±0.015

0.008±0.012

0.002±0.010

0.775±0.363

−0.461±0.326

−0.358±0.345

Amsterdam_Island

0.045±0.028

0.011±0.021

0.001±0.016

0.530±0.416

−0.328±0.428

−0.285±0.448

Crozet_Island

0.045±0.039

0.012±0.030

0.005±0.022

0.780±0.645

−0.579±0.544

−0.506±0.544

All 11 stations

0.056±0.042

0.018±0.024

0.004±0.017

0.662±0.364

−0.297±0.365

−0.183±0.385

a The minus and plus of the mean bias values represent the underestimation and overestimation by the aerosol models relative to the in situ values, respectively.